1. Field of the Invention
The invention relates to marine compasses, particularly with respect to rate-of-turn indicators for gyrocompasses.
2. Description of the Prior Art
Marine gyrocompass systems often include a rate-of-turn indicator as an aid to navigation that displays the rate at which the ship is turning and the direction of turn. It is desirable in certain applications to display rate-of-turn in a discrete format over a wide range of turn rates. For example it is desirable to display turn rate from 0 to 15 degrees per second with a quantized resolution of one degree per second. Available prior art rate-of-turn displays do not provide such capability. One type of prior art device displays rate-of-turn as a relative value not as a discrete. The display is a linear arrangement of light emitting diodes (LEDs) with a common center. When the compass indicates, for example, a clockwise rotation of the vessel, the right half of the line of LEDs beginning at the center sequentially illuminate and remain on until the entire right half side of the LEDs are illuminated. Thereafter, all of the LEDs begin flashing at a frequency proportional to the rate at which the ship is turning. Such a display provides an impression of movement but not actual turn rate values. Another type of available prior art device displays direction and rate-of-turn in a continuous format on an analog meter and only up to one degree per second. This device operates on principles different from that utilized in the present invention.